1. Field of the Invention
The present invention relates to a method of inspecting the interior of a tire with an X-ray and an apparatus used in the method.
2. Description of the Prior Art
Heretofore, for tire internal inspection, a tire has been taken out from the line, a transmission X-ray image of the tire has been taken by an X-ray camera, and the states of bead wires as tire constituent members and the entry of foreign matter such as a micro-metal or small stone into the tire have been visually checked from the obtained transmission X-ray image of the tire by an operator to judge whether the tire is acceptable or not. In this method in which tires are take out one by one, the production line must be suspended each time inspection is made, thereby reducing productivity. Therefore, the tire internal inspection has to be sampling inspection. In addition, since the work of judging whether a tire is acceptable or not is carried out by operator's visual inspection, the result of judgment is apt to be affected by the skill of each operator and differ by each individual operator.
To cope with these problems, the inventors of the present invention have proposed a method of automating the internal inspection of all the tires in Unexamined Japanese Patent Application No. 2000-249665. As shown in FIGS. 7(a) and 7(b), an X-ray tube 2 and an X-ray generator 3 for driving this X-ray tube 2 are installed at predetermined positions above a roll conveyor 1 for conveying vulcanized tires 10, an X-ray line sensor 4 is arranged in the space between adjacent rolls 1R and 1R below the above roll conveyor 1 at a position corresponding to the X-ray tube 2 to detect an X-ray which has been applied from the above X-ray tube and has passed through the tire 10 conveyed by the roll conveyor 1 in order to take a transmission X-ray image of the above tire continuously, the obtained transmission X-ray image is supplied to the image processing unit 50a of tire internal image inspection means 50 to be processed, and an X-ray image of a normal tire pre-stored in storage means 50b is compared with the above obtained image by a judging unit 50c to judge whether the tire 10 is acceptable or not. This makes it possible to automate the internal inspection of all the tires efficiently without suspending the production line. In the above figures, reference numeral 6 denotes a slit for narrowing the optical path of the applied X-ray, and 7 and 8 denote a lead shield box and a lead curtain installed to prevent an X-ray from leaking from the measurement area to the outside, respectively.
In order to increase the speed and maneuverability by improving the cornering power of a car tire, the tire now tends to have a lower profile. However, in the above method, when a low profile tire such as 205/55 R16 or 215/50 ZR17 is internally inspected, as shown in FIG. 8, the area where images of bead wires 11 and tread belts 12 which are metal members are superimposed becomes large. The portions which become the dead areas of the above metal members are dead areas 11x formed by the bead wires 11 and a dead area 12x formed by the tread belt 12x, all shown in black in the figure and become shadows after image processing. Therefore, even when foreign substances p and q such as metals are existent between the bead wire 11 and the tread belt 12, they cannot be identified and the inspection accuracy is thereby reduced.
Then, as shown in FIG. 9, it is conceivable that the conveyance of the tire 10 is suspended, the tire 10 to be inspected is grasped by a chuck 15, and a transmission X-ray image of the tire is taken while it is turned in order to take a transmission X-ray image of a portion included in the above dead areas 11x and 12x. However, as inspection takes too long in this method, it cannot be said that this method is practical.
It is an object of the present invention which has been made in view of the problems of the prior art to provide an X-ray tire inspection method and apparatus capable of carrying out the internal inspection of even a tire having a low aspect ratio accurately and efficiently.